Joysticks are well-known devices to transfer a pilot's manual input commands to various aircraft flight control surfaces. In their early forms, joysticks were usually mounted on the cockpit floor between the pilot's legs. They were typically mounted so as to enable compound pivotal movement of the stick about two mutually-perpendicular axes, representing the pitch and roll axes of the aircraft. However, the position and size of these joysticks often interfered with other devices and freedoms, and required considerable space to accommodate the range of permissible movement of the handle.
Originally, such joysticks were connected to various airfoil surfaces by mechanical linkages and cables. These couplings were unnecessarily heavy and bulky, and did not readily allow for redundancy.
As the performance, control and sophistication of aircraft have increased, fly-by-wire systems have been developed. In these systems, various manual inputs to the joystick handle are first transduced into electrical signals, and these are then transmitted along various redundant paths to one or more computers, and then to remotely-located motors and drivers that control movement of the various airfoil surfaces. Thus, mechanical transmittals from joysticks and column wheels have given way to electrical transmittals from transducers associated with the sticks.
In more recent years, side-sticks have been developed. These are typically mounted ahead of an arm rest located on the outboard sides of the pilot's and co-pilot's seats. The pilot is typically seated in the left seat, and the co-pilot in the right seat. Thus, the pilot's side-stick us usually to his left, and the co-pilot's side-stick us usually to his right. Hence, the pilot will typically rest his left arm on his left arm rest, and will control his side-stick with his left hand, while the co-pilot will typically rest his right arm on his right arm rest, and will control his side-stick with his right hand. In many cases, the tilting of the stick about the appropriate axis was sensed as a function of position (see, e.g., U.S. Pat. Nos. 5,125,602 and 5,291,113). In other cases, it was sensed as a function of force or torque (see, e.g., U.S. Pat. Nos. 6,028,409; 5,694,010 and 5,347,204).
Some of these side-sticks have been mounted on gimbals to allow for omni directional or compound pivotal movement about the pitch and roll axes (see, e.g., U.S. Pat. Nos. 5,291,113 and 5,694,014).
Side-sticks are typically thought of as being either “passive” or “active”. A “passive” side-stick unit (“PSSU”) senses the pilot's or co-pilot's pitch and roll commands as functions of the tilting displacement of the associated control stick about the appropriate axes. These commands are then supplied to one or more flight control computers, which, in turn, control the movement of various airfoil surfaces to control the pitch and roll of the aircraft. The control stick may supply redundant command signals to the computer. Some of these devices use various springs to apply various force-feel gradients to the handle of the control stick to afford the pilot and copilot a tactile sensation and feel of various conditions (see, e.g., U.S. Pat. No. 5,125,602).
An “active” side-stick unit (“ASSU”) is similar to a PSSU, but further incorporates motors to couple the positions of the pilot's and co-pilot's side-sticks. If the pilot is actively controlling the aircraft, and the co-pilot has his hand off his stick, the co-pilot's stick will be back-driven to follow and duplicate the various positional movements that the pilot supplies to his stick. Thus, the pilot's and co-pilot's sticks will tilt simultaneously in parallel and in unison, as if one were slaved to the other. Conversely, if the co-pilot is actively controlling the aircraft, and the pilot has his hand off his stick, the pilot's stick will follow and duplicate the positional commands supplied by the co-pilot to his stick. This is sometimes known as “position recopying” (see, e.g., U.S. Pat. No. 5,125,602), or an “electrical cross-cockpit interconnect” (see, e.g., U.S. Pat. No. 5,456,428), or simply “cross-coupling” (see, e.g., U.S. Pat. No. 5,694,014).
If the aircraft is provided with an autopilot, the autopilot may generate electrical signals that are supplied to the motors associated with the pilot's and co-pilot's control sticks to back-drive both of these sticks.
It is also known to provide such side-sticks with various feedback force sensations that simulated the “feel” of the resistance of the airfoil surfaces to the various input commands, or the transitions between various operational conditions, or even a vibration in the case of an emergency. It is also known to damp such control sticks so as to impede the stick from freely moving from a manually-commanded position if the operator were to let go of the stick (see. e.g., U.S. Pat. Nos. 5,125,602; 6,459,228 and 4,069,720). The aggregate disclosures of each of the foregoing patents is hereby incorporated by reference.
However, the column wheels, joysticks and side-sticks developed heretofore have involved various mechanical linkages and couplings that have introduced friction, backlash, and the like into the movement of the control stick. These designs are believed to have been heavy and bulky. They are believed to have interfered with the smooth continuous transmission of manual pilot input signals from the control stick to the flight control computer, and with the smooth continuous transmission of various electrical signals to back-drive the control stick in accordance with the electrically-commanded movements and forces.
Accordingly, there is believed to be a demonstrated and long-felt need to provide improved control sticks that are adapted for use in both “passive” and “active” fly-by-wire flight control systems, and for improved linkages for use with such improved control sticks, and for improved compound torsional springs for possible use therein.